Stephen Hawking gives his support to Breakthrough Listen, an intensive search for alien life

Astronomers are to embark on the most intensive search for alien life yet by listening out for potential radio signals coming from advanced civilisations far beyond the solar system.

Leading researchers have secured time on two of the world’s most powerful telescopes in the US and Australia to scan the Milky Way and neighbouring galaxies for radio emissions that betray the existence of life elsewhere. The search will be 50 times more sensitive, and cover 10 times more sky, than previous hunts for alien life.

The Green Bank Observatory in West Virginia, the largest steerable telescope on the planet, and the Parkes Observatory in New South Wales, are contracted to lead the unprecedented search that will start in January 2016. In tandem, the Lick Observatory in California will perform the most comprehensive search for optical laser transmissions beamed from other planets.

Operators have signed agreements that hand the scientists thousands of hours of telescope time per year to eavesdrop on planets that orbit the million stars closest to Earth and the 100 nearest galaxies. The telescopes will scan the centre of the Milky Way and the entire length of the galactic plane.

The Breakthrough Listen launch at the Royal Society. The project will be the most comprehensive search for radio and optical signals coming from intelligent life beyond the solar system

Launched on Monday at the Royal Society in London, with the Cambridge cosmologist Stephen Hawking, the Breakthrough Listen project has some of the world’s leading experts at the helm. Among them are Lord Martin Rees, the astronomer royal, Geoff Marcy, who has discovered more planets beyond the solar system than anyone, and the veteran US astronomer Frank Drake, a pioneer in the search for extraterrestrial intelligence (Seti).

Stephen Hawking said the effort was “critically important” and raised hopes for answering the question of whether humanity has company in the universe. “It’s time to commit to finding the answer, to search for life beyond Earth,” he said. “Mankind has a deep need to explore, to learn, to know. We also happen to be sociable creatures. It is important for us to know if we are alone in the dark.”

The project will not broadcast signals into space, because scientists on the project believe humans have more to gain from simply listening out for others. Hawking, however, warned against shouting into the cosmos, because some advanced alien civilisations might possess the same violent, aggressive and genocidal traits found among humans.

“A civilisation reading one of our messages could be billions of years ahead of us. If so they will be vastly more powerful and may not see us as any more valuable than we see bacteria,” he said.

The alien hunters are the latest scientists to benefit from the hefty bank balance of Yuri Milner, a Russian internet billionaire, who quit a PhD in physics to make his fortune. In the past five years, Milner has handed out prizes worth tens of millions of dollars to physicists, biologists and mathematicians, to raise the public profile of scientists. He is the sole funder of the $100m Breakthrough Listen project.

“It is our responsibility as human beings to use the best equipment we have to try to answer one of the biggest questions: are we alone?” Milner told the Guardian. “We cannot afford not to do this.”

Milner was named after Yuri Gagarin, who became the first person to fly in space in 1961, the year he was born.

Let's listen out for alien life – and remember we might not understand it

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The Green Bank and Parkes observatories are sensitive enough to pick up radio signals as strong as common aircraft radar from planets around the nearest 1,000 stars. Civilisations as far away as the centre of the Milky Way could be detected if they emit radio signals more than 10 times the power of the Arecibo planetary radar on Earth. The Lick Observatory can pick up laser signals as weak as 100W from nearby stars 25tn miles away.

Marcy, at the University of California, Berkeley, said: “We look across the landscapes of the other worlds within our solar system, now including Pluto, and see no intelligent life. The worlds within our solar system show no city lights, no road systems, and no obelisks of generations long gone.”

“Our loneliness within our solar system makes it natural to look beyond, to stars and galaxies, to search for communicative folks. We hope to learn if we are alone or if, instead, we may join in a large collective of sentient beings with whom to share this universe,” he added.

The Parkes Observatory radio telescope in New South Wales, Australia. Photograph: Ian Waldie/Getty Images

Engineers will build digital processing equipment to handle the vast amount of data the telescopes will collect, allowing them to search through billions of cosmic radio channels simultaneously. The software will be open source, and all of the radio emissions the telescopes pick up will be released to the public. The 9 million volunteers around the world who donate computer time to the SETI@home project, will help sift the data for signals that are not from natural sources.

There are plenty of heavenly objects that can be confused with the broadcasts of alien civilisations. In 1967, the astronomer Joceyln Bell Burnell spotted rapid, regular radio pulses coming from a region of space. For fun, the signal was dubbed LGM-1, short for Little Green Men. But the transmissions were later traced to a spinning neutron star, and marked the discovery of pulsating radio stars, or pulsars.

Andrew Siemion, director of the Berkeley Seti Research Center, said the Breakthrough Listen project would be the first to scan the entire range of a crucial 10GHz frequency band. “We can now do huge chunks of radio bandwidth all at one go,” he said. “These telescopes are going to be much more sensitive and comprehensive than searches in the past thanks to the dramatic increase in our computational capabilities.”

Dan Werthimer, chief scientist on the SETI@home project, said that since some stars are twice the age of the sun, there may be planets around them that are home to civilisations many billions of years more advanced than humanity. Alien civilisations could be leaking radio emissions, in the same way TV broadcasts and radar signals on Earth spread out into space. Or they could be transmitting greetings into the space in the hope that someone is listening.

If astronomers detect a signal that bears the hallmarks of a technological society, the first step is to confirm it from a second observatory. “Before you make a big announcement, you need independent verification. It could just be a bug, or a graduate student playing a prank,” Werthimer said. Any message that is verified then needs to be deciphered.

“For thousands of generations people have been asking: are we alone? The answer is profound either way. If we find that the universe is teeming with life, we can learn how they get through their bottlenecks when they were killing each other, and we can become part of the galactic civilisation. But it’s also profound if we are alone. If that’s the case, we’d better take pretty damn good care of life on this planet,” Werthimer said.

Lewis Ball, director of astronomy and space science at the Commonwealth Scientific and Industrial Research Organisation in Australia, said: “The Parkes radio telescope is essential for the scientific integrity of the programme through providing coverage of the southern sky. Its huge size and excellent receiver technology enables it to detect exquisitely weak signals that may provide evidence of intelligent life elsewhere in the universe.”

“The likelihood of finding extraterrestrial intelligence through this new programme is higher than in any previous search but is still extremely low, but the impact of such a discovery would be as high or higher than any other scientific result that can be contemplated.

“The new Seti programme will help to secure the availability of the capabilities of the Parkes Observatory for other astronomers and will not displace any other high priority astronomy projects,” he added.

Drake said: “Right now there could be messages from the stars flying right through the room, through us all. That still sends a shiver down my spine. The search for intelligent life is a great adventure. And Breakthrough Listen is giving it a huge lift.”

A second initiative, called Breakthrough Message, establishes an international competition open to all-comers to create digital messages, encoding a description of humans, our civilisation, and planet. The signals will not be beamed into space, but Milner hopes the challenge will spur a debate about how to communicate with alien life, and the ethical and philosophical issues involved.